1. Field of the Invention
The present invention relates to an image display apparatus, a multi display system, a coordinate information output method, and a program for implementing the method.
2. Description of the Related Art
A coordinate information output device has been used as a device for inputting coordinate information to a personal computer, and is divided into two types: one that handles relative coordinates such as a mouse, and the other that handles absolute coordinates such as an on-screen digitizer.
A mouse is horizontally moved on a flat surface of a desk or the like to obtain and input its relative movement amount to a personal computer as coordinate information. This causes the cursor or pointer (hereinafter generically referred to as “the cursor”) on the display screen to be moved by the movement amount from the present cursor position. When a mouse button is clicked (pressed and released), the mouse inputs its click operational information to the personal computer.
On the other hand, an on-screen digitizer is equipped with a coordinate input screen, a pointing means for pointing desired positions on the coordinate input screen (hereinafter generically referred to as “the pen”), and a coordinate position detecting means for detecting the positions pointed by the pen as absolute coordinates corresponding one-to-one to the coordinate input screen. This on-screen digitizer is connected to a personal computer to input the coordinate information of a position on the coordinate input screen pointed by the pen. This causes the cursor on the display screen to be moved to the pointed position. Further, the on-screen digitizer inputs its operational information to a personal computer by operating a switch provided on a pen and corresponding to a mouse button or by touching the display screen by the pen.
A click operation by the mouse button corresponds to a pen-down and pen-up operation onto the coordinate input screen in the on-screen digitizer. A mouse drag operation (moved while the button is pressed) corresponds to a movement of the pen in the pen-down state on the coordinate input screen of the on-screen digitizer. The termination of the mouse drag operation corresponds to a pen-up operation in the on-screen digitizer. Incidentally, if the pen goes outside of the coordinate input area, the digitizer recognizes the situation as a pen-up.
In accordance with the recent expanding usage opportunities of personal computers, these coordinate information output devices are selectively used as the situation demands.
For example, PC operating systems (OS), the “Windows 98” version and subsequent versions, made by Microsoft Corporation, U.S.A. are provided with a multi display function for dividing the screen of one personal computer into screens for a plurality of displays, enabling to increase the displaying capacity.
In using such a multi display function, there can be such a case where the operating range of a mouse may extend over screens for a plurality of displays. For example, a case where a file on the screen area of the first display is shifted to the screen area of the other display by a drag operation, or a case where a line is drawn over screen areas of a plurality of displays using a drawing application.
A mouse, which is for inputting relative coordinates, is rather easy to operate over a plurality of displays. On the other hand, an on-screen digitizer, which is for inputting absolute coordinates, cannot operate over a plurality of displays.
Because of this, some on-screen digitizers have a digitizer controller provided separately from a plurality of displays, in order to cover the operation of coordinate designation over the plurality of displays (e.g. Japanese Laid-Open Patent Publication (Kokai) No. H08-286835).
The above-mentioned digitizer controller is provided as a separate device for a multi display system that is comprised of a plurality of displays. Therefore, if the displays are provided with respective on-screen digitizers, the multi display system has a redundant dual structure.
However, in the above multi display system that is comprised of a plurality of displays that are provided with respective on-screen digitizers, each of the on-screen digitizers inputs absolute coordinates corresponding one-to-one to the corresponding display screen, as a coordinate input screen, to a personal computer. Therefore, when an operation is carried out over a plurality of displays, the continuity of the coordinate input area is interrupted at the frames of the display screens. As a result, it is impossible to conduct a drag operation over a plurality of displays.